Polyurethane encapsulated fertilizer

ABSTRACT

A polyurethane encapsulated, slow release fertilizer with a coating based upon an isocyanate component and an isocyanate-reactive component comprising a polyether polyol. The process for producing such particles comprises applying an isocyanate-reactive component comprising a polyether polyol onto fertilizer particles to form coated fertilizer particles, applying an isocyanate component onto said coated fertilizer particles; and forming the polyurethane encapsulated fertilizer particles.

FIELD OF THE INVENTION

This invention relates to the art of fertilizer and, more particularly,to a coated granular fertilizer in which the dissolution rates ofwater-soluble fertilizer components are controlled by coating orencapsulating a granular fertilizer.

BACKGROUND OF THE INVENTION

Achieving crop fertilization by timing the release or application offertilizer nutrients is known. Fertilization in the container-grownwholesale plant industry, for example, has been accomplished by methodsincluding:

-   -   Multiple applications of granular fertilizer    -   Overhead liquid application of soluble fertilizers    -   Incorporating slow release fertilizers into potting soil    -   Polymer coated fertilizers.

Each of these methods and compositions has associated drawbacks. Adescription of the drawbacks associated with prior art methods andcompositions can be found in U.S. Pat. application Ser. No. 10/973,732,which is incorporated in its entirety herein.

Encapsulating fertilizers to slowly release nutrient to plants is known.Slow release fertilizers delay the dissolution of the fertilizersubstrate. Most slow release fertilizers, however, are not dependable inadverse environmental conditions such as high heat and moisture. Hot andwet conditions can cause slow release fertilizers to flash release,causing damage to both the plant material and the environment.

Prior art methods include encapsulating a fertilizer having a givenchemical composition or compound such that the nutrients are releasedover a period of time. For example, coated urea has been used as asource of time released nitrogen, which is a nutrient that promotesplant height and leaf formation in a plant. U.S. Pat. Nos. 5,147,442,5,560,768 and 6,500,223 each of which is incorporated in its entirety,illustrate such coated fertilizers and methods associated with them.[0006] Encapsulated slow-release fertilizers may be classified into twomajor groups according to the fertilizer release mechanism:

(i) A first group in which the release is governed by the rate of waterpermeation through a polymeric or copolymeric membrane of thewater-proofing material, and by the rate of fertilizer diffusion awayfrom each coated particle into the surrounding soil. Typical examples ofmembrane material in slow-release fertilizers of this group arecopolymers or glyceryl esters of unsaturated acids withdicyclopentadiene (U.S. Pat. No. 3,223,518), epoxy-polyester resins(U.S. Pat. No. 3,259,482), urethanes (U.S. Pat. No. 3,264,089) andpolystyrenes (U.S. Pat. No. 3,158,462).

(ii) A second group with relatively thick encapsulating coats, in whichrelease is governed mainly by rupture of the coat, a typical examplebeing particulate fertilizers with sulfur based encapsulation. Therupture occurs upon the permeation of water into the coated particles asa result of the osmotic pressure that builds up within. The sulfur basedcoating in slow-release fertilizers of this second group are generallyproduced by spraying onto the particulate fertilizer a molten sulfurbased material as disclosed, for example, in U.S. Pat. No. 4,857,098.

Inefficient fertilization using past existing polymer coated fertilizersdescribed at (i) and (ii) above increases costs and losses with respectto crops. In order to achieve the safe release of nutrient, currentslow-release coated fertilizers must be relatively thickly coated, asmeasured by percentages of weight. Thicker coatings are necessarily morecostly as result of, inter alia, the need for more coating materials.What is needed is an encapsulated slow-release fertilizer that cansafely release nutrient to plants using coating that is more efficient.

SUMMARY OF THE INVENTION

The present invention provides a process for producing polyurethaneencapsulated, slow-release fertilizer particles. The process comprisesapplying an isocyanate-reactive component that includes a polyetherpolyol onto fertilizer particles to form a coating on the fertilizerparticles, and applying an isocyanate component onto said fertilizerparticles. The applications of each component may be repeated so as toform the polyurethane encapsulated fertilizer particles comprising up toabout nine percent of said coating by weight.

Another embodiment provides coated granular fertilizer comprisingpolyurethane encapsulated, slow release fertilizer particles comprisinga coating of up to about six percent of said coating by weight, saidwherein the coating releases nutrient from a nutrient substrate. Theconditions for each of the nutrient release rates below are at 100degrees Fahrenheit - (e.g.: nitrogen release at about 1,120 ppm at 100degrees Fahrenheit). The nutrient substrate can include potassiumnitrate in the percentages of 12-0-43 (N-P-K) at release ratescomprising from about 1,120 ppm to about 35,000 ppm of nitrogen in aboutone day, from about 5,200 ppm to about 74,000 ppm of nitrogen in aboutthree days, and from about 10,500 ppm to about 104,000 ppm of nitrogenin about seven days. The coated fertilizer also can release from about1,000 ppm to about 15,000 ppm of potassium in about one day, from about3,000 ppm to about 170,000 ppm of potassium in about three days, andfrom about 19,000 ppm to about 212,000 ppm of potassium in about sevendays.

The nitrogen release of this coated fertilizer at about four percent ofthe coating is about 17,200 ppm of nitrogen in about one day, about74,000 ppm of nitrogen in about three days, and about 104,000 ppm ofnitrogen in about seven days. At about five percent of the coating byweight the coating releases nutrient at rates comprising about fromabout 14,600 ppm to about 35,000 ppm of nitrogen in about one day, fromabout 41,500 to about 58,000 ppm of nitrogen in about three days, andfrom about 58,000 to about 94,000 ppm of nitrogen at 100 degreesFahrenheit in about seven days. Nitrogen release at about six percent ofsaid coating by weight is from about 1,120 ppm to 12,400 ppm of nitrogenin about one day, from about 8,600 ppm to about 36,000 ppm of nitrogenin about three days, and from about 16,500 ppm to about 54,200 ppm ofnitrogen in about seven days. When the coating is about eight percent byweight, nitrogen release rates comprise about 2,300 ppm in about oneday; about 5,200 ppm in about three days; and about 10,500 ppm in aboutseven days.

As regards potassium release, when the coating of the granularfertilizer is about four percent of the coating by weight the coatingreleases potassium at rates comprising about 12,000 ppm of potassium inabout one day, about 170,000 ppm of potassium in about three days, andfrom about 212,000 ppm of potassium in about seven days. At about fivepercent of the coating by weight, the release rates comprise from about12,000 ppm to about 15,000 ppm of potassium in about one day, from about45,000 ppm to about 120,000 ppm of potassium in about three days, andfrom about 110,000 ppm to about 184,000 ppm of potassium in about sevendays. Potassium release rates at about six percent of the coating byweight comprise: from about 1,000 ppm to about 10,000 ppm of potassiumin about one day, from about 3,000 ppm to about 90,000 ppm of potassiumin about three days, and from about 19,000 ppm to about 105,000 ppm ofpotassium in about seven days. When the coating is about eight percentby weight, potassium release rates comprise about 1,000 ppm in about oneday; about 4,000 ppm in about three days; and about 19,000 ppm in aboutseven days.

The polyurethane encapsulated, slow release fertilizer's coating can bebased upon an isocyanate component and an isocyanate-reactive componentcomprising a polyether polyol.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall block flow diagram of the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The coated granular fertilizer according to the invention can comprise aparticulate fertilizer to be covered with a resin composition. Theparticulate fertilizer used in the present invention is not criticalwith respect to the type and may be any known chemical fertilizer.Examples of the fertilizer include ammonium sulfate, ammonium chloride,ammonium nitrate, urea, potassium chloride, potassium sulfate, potassiumnitrate, sodium nitrate, ammonium phosphate, potassium phosphate,calcium phosphate, and composite fertilizers thereof.

The granular fertilizer is coated with a water-resistant film-formingpolyurethane composition. The composition should comprise aisocyanate-reactive polyether polyol and an isocyanate component, andoptionally, other polymers, waxes, inorganic and organic powders andsurface active agents. The waxes used in the present invention may beany waxes provided that they are soluble in solvents for the essentialpolymers. Examples of such waxes include paraffin wax, hardened oils,bee wax, Japan wax, rosin, petroleum resins and the like.

The invention provides compositions and methods for delivering theproper nutrition to plants by the encapsulation of fertilizer particles.The term “fertilizer” as used herein denotes an at least moderatelywater-soluble chemical substance or mixture of such substances, and theterm “particulate fertilizer” used herein denotes any type of comminutedfertilizer such as granulated, pelleted, or microgranulated and thelike. Nutrient releases is described in terms of parts per million (ppm)at about plus (+) or minus 20% (−) of the ppm given (i.e. + or−1,000 ppmof potassium release).The following examples further illustrate detailsfor the process of the present invention, and the preparation of thecompositions of this invention. The invention, which is set forth inthis disclosure, is not to be limited either in spirit or scope by theseexamples. Those skilled in the art will readily understand that knownvariations of the conditions and processes of the following preparativeprocedures can be used to prepare these compositions. Unless otherwisenoted, all temperatures are degrees Celsius and all parts andpercentages are parts by weight and percentages by weight, respectively.

EXAMPLES

Polyol: a polyether polyol obtained by adding propylene oxide to aglycerine nucleus. The polyol has a hydroxyl number of from about 388 toabout 408, a nominal functionality of about 3; and a nominal molecularweight of about 400. Its density in lbs/gallon at 77 degrees Fahrenheitis about 8.75; at 100 degrees Fahrenheit is about 8.68 and at 120degrees Fahrenheit is about 8.61. The polyol's viscosity is about 360cps at 77 degrees Fahrenheit, about 160 cps at 100 degrees Fahrenheit,and about 78 cps at 120 degrees Fahrenheit. It has a specific heat of0.5 BTU/lb Fahrenheit, and a thermal conductivity of 0.087 BTU/lb ft²Fahrenheit/in. An exemplary polyol is commercially available as BASFPlurocol GP430.

Isocyanate: A polymethylene polyphenylpolyisocyanate having a NCOcontent of about 31.5% by weight, a viscosity of about 200 cps, at about25 degrees, a hydrolyzable chlorine of about 0.035% by weight, a flashpoint of about 200 degrees, density of about 1.23 g/cm³ at about 25degrees, an initial boiling point of about 190 mm Hg at about 25degrees; and vapor pressure of about 0.0002 mm Hg at about 25 degrees.The isocyanate is a polymeric MDI with a functionality of about 2.7 Anexample is commercially available as BASF Lupranate M20S

Encapsulation of Fertilizer Pellets:

Among other things, compositions and methods of the present inventioncan provide proper nutrition to plants in the differing stages of plantgrowth. In a non-limiting example, semi-permeable resin membranesencapsulate particulate fertilizers. The membranes differ in porosity.The porosities are matched to the solubility of each specific nutrientto control the speed of release. During manufacturing, the thickness ofthe resin coating together with the choice of resin type coatingmembrane, creates the release criteria. The fertilizer substratereleases by timed osmosis back through release channels of thesemi-permeable membrane, providing the corresponding nutrient to thecrop. By matching each nutrient to a given porosity of the membranes, aswell as adjusting resin thickness, the process individually controls thetime release of each nutrient such at least one plant receives theappropriate fertilizer nutrient at the differing stages of the a plant'sgrowth. A description of proper nutrition in a plant in the differingstages of plant growth as well as exemplary methods and compositions forproviding such nutrition can be found in U.S. Pat. application Ser. No.10/973,732, incorporated herein.

FIG. 1 is an overall block flow diagram of the method of the invention.The method begins by introducing the fertilizer particles into a rotaryblender 100. In one example, 50 lbs of substrate potassium nitrate isintroduced into the blender. The substrate is then heated 110 toapproximately 60 degrees for time sufficient to drive all moisture outof the material.

An isocyanate-reactive polyether polyol is applied onto the fertilizerparticles to form a coating on said fertilizer particles 120. Forexample, two ounces of the polyol component (Plurocol) can be added tothe substrate. No pressure is used, and the material is slowly pouredonto the substrate while the rotary blender is in operation. Therelatively low viscosity of the polyol allows rapid and even coverage ofall the substrate particles. Next, the isocyanate component is appliedto the fertilizer 130. In the example, after 2 minutes of blending, theisocyanate (Lupranate) binder is introduced, again by simply pouring itinto the agitating material. Complete reaction can occur within about 6to 7 minutes without any clumping of the processed substrate at any timeduring the reaction. This process can then be repeated 140, withoutincreasing the rate of application. Modifications may includepre-sealing the substrate material with vegetable oil or polyethylene,and/or using an outer layer of wax or polyethylene to extend releasetime. Analysis of these examples made via the method are shown in Table1.

In another example, five (5) batches of polyurethane encapsulatedfertilizer are made using following procedure. A potassium nitratesubstrate of 13.5-0-45 (N-P-K) is heated about 225 degrees F., with thetemperature kept constant a plus or minus 15 degrees throughout process.A fine granular matter, such as ionized iron oxide pigment, may then beadded at .5% to the heated substrate. Then .5% canola oil may be added.This seals imperfections in the individual prills, allowing the polymersto form completely around each prill. The use of the vegetable oil (e.g.canola) in this process eliminates premature or “flash release” ofnutrients, which can cause burn to plants. The addition of iron oxide isalso coloring process, giving the prills a brownish red color. Pluracolis then added at 0.75% and allowed to mix thoroughly. Then 0.75% of thelupranate is added. Reaction time is complete in 7-8 minutes at theheated temperature, and the momentary clumping does not occur at thistemperature. This process may then be repeated 3 more times, with eachaddition of polymer weighed carefully, so the final product has 6 lbs ofpolymer reacted. By calculated weight, the polymer coating is 6/107lbs.,or 5.6%. (With respect to the polymer coated potassium nitrate, thepercentages of 12-0-43, as used herein, are shown using this example.Beginning with 100 lbs of 13.5-0-45, then the final analysis would be100/107 ×13.5-0-45, which is 12.6-0-42.05. Primary nutrients (N-P-K) areexpressed as whole numbers, so the percentages are expressed as12-0-42.) Analysis of these examples is shown in Table 3. Analysis:

Using this process, one set of samples of the polyurethane encapsulatedfertilizer particles beginning with the initial coating of about 0.5% upto about 6% coating by weight were retained. Beginning with the coatingat about the 3% level, after 12 days in room temperature water, prillfailure rate was less than 3% of the prills, going down to the 6%coating, which exhibited two (2) prills which became soft and floated upafter stirring the sample of 2 tbsp in 6 oz of water. Thesamples'demonstrated resistance to prill failure shows that the coatedfertilizer is not subject to unsafe flash release.

Samples of polyurethane encapsulated fertilizer particles with the 3%,4%, 5% and 6% coatings were compared to 2 month (H2), 4 month (H4), and8 to 9 (P8) month coated time released potassium nitrate commerciallyavailable from Haifa and Pursell. All of the compared coated fertilizersincluded time released potassium nitrate at the percentages of 12-0-43(N-P-K) as the fertilizer substrate. The results of the comparison ofthe exemplary polyurethane encapsulated fertilizer particles of thepresent invention at 4% (A4), 5% (A5) and 6% (A6) levels of coating areshown below in Table 1.

With respect to the 2 to 3 month Haifa product (H2) vs. the A4 sample,the A4 demonstrated tighter release at day one. All nutrient release wastrialed at 100 degrees Fahrenheit. As shown in Table 1 below, A4released Nitrogen at 17,200 parts per million (ppm) versus H2's Nitrogenrelease at 36,200 ppm; A4's potassium release was 12,000 ppm versus H2's90,000 ppm. This indicates that the A4 can perform very well even atabout a 3.5% level of coating. A4 showed to be still tighter than H2 atthe 7 day level, since A4 released Nitrogen at 104,000 ppm versus H2'sNitrogen release at 111,600 ppm and A4's potassium release of 212,000ppm versus H2's 224,000 ppm.

When compared to the 4 to 5 month Haifa product (H4), the A5 sample wasso much tighter that a coating of up to from about 4% to about 4.5%could safely be used over the same time period as the H4 product.

As regards the A6 sample when compared to the 8 to 9 month Polyon (P8),the A6 sample demonstrated comparable results through the 3 and 7 dayresults, although the A6 more slowly released nutrient. The slowerrelease of nutrient indicates that there may be up to thirty dayslongevity in field performance.

The results in Table 1 below show that the encapsulated fertilizerparticles of the present invention have tighter upfront release ofnutrient, which demonstrates complete safety to plants. The comparativeresults are set forth in Table 1 below. It is seen that the conductivityvalues, the measurement of low soluble salts, go down with eachadditional layer of polymer, indicating that release longevity can becontrolled by amount of polymer added. Also, the encapsulated fertilizerparticles when placed in water for 3 weeks showed no susceptibility toflash release. TABLE 1 NUTRIENT RELEASE AT 100° F. SAMPLE ID PARAMETERUNIT DAY 1 DAY 3 DAY 7 A4 12-0-43 Nitrogen ppm 17,200 74,000 104,000Potassium ppm 12,000 170,000 212,000 Conductivity mmhos/cm 92.00 658.00900.00 A5 12-0-43 Nitrogen ppm 14,600 58,000 94,400 Potassium ppm 12,000120,000 184,000 Conductivity mmhos/cm 102.00 520.00 740.00 A6 12-0-43Nitrogen ppm 12,400 36,000 54,200 Potassium ppm 10,000 90,000 114,000Conductivity mmhos/cm 60.00 248.00 452.00 H2 12-0-43 Nitrogen ppm 36,20098,000 111,600 Potassium ppm 90,000 206,000 224,000 Conductivitymmhos/cm 682.00 874.00 960.00 H4 12-0-43 Nitrogen ppm 34,000 74,00084,600 Potassium ppm 70,000 176,000 192,000 Conductivity mmhos/cm 504.00700.00 818.00 P8 12-0-43 Nitrogen ppm 13,800 38,000 56,800 Potassium ppm20,000 82,000 118,000 Conductivity mmhos/cm 148.00 342.00 486.00

The results in Table 2 below show that the encapsulated fertilizerparticles of the present invention have tighter upfront release ofnutrient, which demonstrates complete safety to plants. In the examplesset forth, the coating was up to about eight to nine percent. Thecoating percentages are listed in the table. Among other things, these 5exemplary results indicate that a coating of 6% can be designed torelease over 9 months. TABLE 2 NUTRIENT RELEASE AT SAMPLE 100° F. IDPARAMETER UNIT DAY 1 DAY 3 DAY 7 Fertilizer A - 11-8 Nitrogen ppm 5,6007,400 11,600 (At about 8%) Potassium ppm 2,000 3,000 23,000 Conductivitymmhos/cm 14.00 20.00 120.00 Fertilizer A - 11-9 Nitrogen ppm 6,600 7,60012,000 (At about 9%) Potassium ppm 3,000 4,000 184,000 Conductivitymmhos/cm 19.00 27.00 110.00 Fertilizer A - 15-4 Nitrogen ppm 35,00041,500 58,000 (At about 5%) Potassium ppm 15,000 45,000 110,000Conductivity mmhos/cm 96.00 226.00 596.00 Fertilizer A - 15-6 Nitrogenppm 5,600 8,600 16,500 About 6%) Potassium ppm 1,000 3,000 56,000Conductivity mmhos/cm 4.00 23.00 232.00 Fertilizer A - 15-8 Nitrogen ppm2,300 5,200 10,500 (About 8%) Potassium ppm 1,000 4,000 19,000Conductivity mmhos/cm 10.00 30.00 111.00 SAMPLE ID PARAMETER UNIT ResultDetection Limit Fertilizer A - 15-8 Total Nitrogen % 13.06 0.10 (N)Soluble Potash % 40.01 0.01 (K2O) Iron (Fe) % 0.16 0.01

The following results shown in Table 3, which all include example of12-0-43 potassium nitrate at 6% coating by weight, also demonstrateexamples of the consistency of fertilizer release at 100 degrees inwater bath for and through 7 days. When placed in water at roomtemperature for 6 days, there was no prill failure. Samples of theproducts were sent to lab for accelerated release tests on 6 poundpolymer levels. Tests done on products when the isocyanate-reactivepolyether polyol and isocyanate component were added at 2% per layershowed tendency to agglomerate and lose coating to blender surface, so1.5% maximum has been adopted. The results in Table 3 below also showthat the encapsulated fertilizer particles of the present invention havetighter upfront release of 10 nutrient, which demonstrates completesafety to plants. The measurement of low soluble salts in these resultsconfirm the stability of coating at accelerated temperatures. TABLE 3NUTRIENT RELEASE AT SAMPLE 100° F. ID PARAMETER UNIT DAY 1 DAY 3 DAY 705001 - Fertilizer Nitrogen ppm 1,490 10,000 27,700 12-0-43 Potassiumppm 1,300 12,000 71,000 Conductivity mmhos/cm 18.00 134.00 388.0005002 - Fertilizer Nitrogen ppm 1,760 11,000 23,700 12-0-43 Potassiumppm 2,200 16,000 79,000 Conductivity mmhos/cm 23.00 148.00 413.0005003 - Fertilizer Nitrogen ppm 1,480 10,200 26,900 12-0-43 Potassiumppm 1,200 13,000 96,000 Conductivity mmhos/cm 15.00 130.00 420.0005004 - Fertilizer Nitrogen ppm 1,260 11,600 27,700 12-0-43 Potassiumppm 1,000 14,000 93,000 Conductivity mmhos/cm 13.00 136.00 430.0005005 - Fertilizer Nitrogen ppm 1,120 10,600 28,200 12-0-43 Potassiumppm 900 19,000 104,000 Conductivity mmhos/cm 12.00 151.00 454.00 05006 -Fertilizer Nitrogen ppm 1,380 11,300 25,900 12-0-43 Potassium ppm 1,30021,000 105,000 Polymer Coated Conductivity mmhos/cm 15.00 153.00 448.00

It should be understood that the above description is onlyrepresentative of illustrative embodiments and examples. For theconvenience of the reader, the above description has focused on alimited number of representative examples of all possible embodiments,examples that teach the principles of the invention. The description hasnot attempted to exhaustively enumerate all possible variations or evencombinations of those variations described. That alternate embodimentsmay not have been presented for a specific portion of the invention, orthat further undescribed alternate embodiments may be available for aportion, is not to be considered a disclaimer of those alternateembodiments. One of ordinary skill will appreciate that many of thoseundescribed embodiments, involve differences in technology and materialsrather than differences in the application of the principles of theinvention. Accordingly, the invention is not intended to be limited toless than the scope set forth in the following claims and equivalents.

1. A process for producing polyurethane encapsulated, slow-releasefertilizer particles comprising: a) pre-sealing the fertilizer particlesby applying a fine granular material and a vegetable oil to theparticles b) applying an isocyanate-reactive component consistingessential of a polyether polyol onto fertilizer particles to form coatedfertilizer particles; c) applying an isocyanate component onto saidcoated fertilizer particles of step a); and d) forming the polyurethaneencapsulated fertilizer particles.
 2. The method of claim 1 wherein theapplications of steps a) and b) are executed to form the polyurethaneencapsulated fertilizer particles in increments of 0.5 percent of saidcoating by weight.
 3. The method of claim 1 wherein theisocyanate-reactive component comprises a polyol formed by reacting andalkylene oxide with a glycerine nucleus.
 4. The method of claim 3wherein said alkylene oxide is propylene oxide.
 5. The method of claim 3wherein the polyether polyol's characteristics comprise: a hydroxylnumber of from about 388 to about 408; a nominal functionality of about3; and a nominal molecular weight of about
 400. a viscosity of about 360cps at about 77 degrees Fahrenheit, of about 160 cps at about 100degrees Fahrenheit, and about 78 cps at about 120 degrees Fahrenheit. 6.The method of claim 1 wherein the isocyanate component comprises apolymethylene polyphenylpolyisocyanate.
 7. The method of claim 6 whereinthe polymethylene polyphenylpolyisocyanate comprises characteristicsincluding: a NCO content of about 31.5 percentage by weight; a viscosityof about 200 cps at about 25 degrees Celsius; a hydrolyzable chlorine ofabout 0.035 percentage by weight; a flash point of about 200 degreesCelsius; a density of about 1.23 g/cm³ at about 25 degrees Celsius; aninitial boiling point of about 190 mm Hg at about 25 degrees Celsius;and a vapor pressure of about 0.0002 mm Hg at about 25 degrees Celsius.8. (canceled)
 9. The method of claim 1 wherein the fertilizer particlesare pre-sealed with matter comprising: vegetable oil; or polyethylene.10. The method of claim 1 wherein the method further comprises:additionally applying an outer layer to the polyurethane encapsulatedfertilizer particles.
 11. The method of claim 10 wherein the outer layercomprises: wax; or polyethylene.
 12. The polyurethane encapsulated, slowrelease fertilizer particles produced according to the process ofclaim
 1. 13. A coated fertilizer comprising: polyurethane encapsulated,slow release fertilizer particles comprising a coating of up to abouteight percent of said coating by weight, wherein said coating releasesnutrient from a nutrient substrate including potassium nitrate in thepercentages of 12-0-43 (N-P-K) at rates comprising: from about 1,120 ppmto about 35,000 ppm of nitrogen at 100 degrees Fahrenheit in about oneday; from about 5,200 ppm to about 74,000 ppm of nitrogen at 100 degreesFahrenheit in about three days; and from about 10,500 ppm to about104,000 ppm of nitrogen at 100 degrees Fahrenheit in about seven days.14. The polyurethane encapsulated, slow release fertilizer of claim 13wherein said coating is up to about six percent of said coating byweight, and wherein said coating releases nutrient at rates comprising:from about 1,000 ppm to about 15,000 ppm of potassium at 100 degreesFahrenheit in about one day; from about 3,000 ppm to about 170,000 ppmof potassium at 100 degrees Fahrenheit in about three days; and fromabout 19,000 ppm to about 212,000 ppm of potassium at 100 degreesFahrenheit in about seven days.
 15. The polyurethane encapsulated, slowrelease fertilizer of claim 13 wherein said coating is about fourpercent of said coating by weight, and wherein said coating releasesnutrient at rates comprising: about 17,200 ppm of nitrogen at 100degrees Fahrenheit in about one day; about 74,000 ppm of nitrogen at 100degrees Fahrenheit in about three days; and about 104,000 ppm ofnitrogen at 100 degrees Fahrenheit in about seven days.
 16. Thepolyurethane encapsulated, slow release fertilizer of claim 13 whereinsaid coating is about five percent of said coating by weight, andwherein said coating releases nutrient at rates comprising: from about14,600 ppm to about 35,000 ppm of nitrogen at 100 degrees Fahrenheit inabout one day; from about 41,500 ppm to about 58,000 ppm of nitrogen at100 degrees Fahrenheit in about three days; and from about 58,000 ppm toabout 94,000 ppm of nitrogen at 100 degrees Fahrenheit in about sevendays.
 17. The polyurethane encapsulated, slow release fertilizer ofclaim 13 wherein said coating is about six percent of said coating byweight, and wherein said coating releases nutrient at rates comprising:from about 1,120 ppm to about 12,400 ppm of nitrogen at 100 degreesFahrenheit in about one day; from about 8,600 ppm to about 36,000 ppm ofnitrogen at 100 degrees Fahrenheit in about three days; and from about16,500 ppm to about 54,000 ppm of nitrogen at 100 degrees Fahrenheit inabout seven days.
 18. The polyurethane encapsulated, slow releasefertilizer of claim 14 wherein said coating is about four percent ofsaid coating by weight, and wherein said coating releases nutrient atrates comprising: about 12,000 ppm of potassium at 100 degreesFahrenheit in about one day; about 170,000 ppm of potassium at 100degrees Fahrenheit in about three days; and about 212,000 ppm ofpotassium at 100 degrees Fahrenheit in about seven days.
 19. Thepolyurethane encapsulated, slow release fertilizer of claim 14 whereinsaid coating is about five percent of said coating by weight, andwherein said coating releases nutrient at rates comprising: from about12,000 ppm to about 15,000 ppm of potassium at 100 degrees Fahrenheit inabout one day; from about 45,000 ppm to about 120,000 ppm of potassiumat 100 degrees Fahrenheit in about three days; and from about 110,000ppm to about 184,000 ppm of potassium at 100 degrees Fahrenheit in aboutseven days.
 20. The polyurethane encapsulated, slow release fertilizerof claim 14 wherein said coating is about six percent of said coating byweight, and wherein said coating releases nutrient at rates comprising:from about 1,000 ppm to about 10,000 ppm of potassium at 100 degreesFahrenheit in about one day; from about 3000 ppm to about about 90,000ppm of potassium at 100 degrees Fahrenheit in about three days; andabout 56,000 ppm to about 105,000 ppm of potassium at 100 degreesFahrenheit in about seven days.
 21. The polyurethane encapsulated, slowrelease fertilizer of claim 13 wherein said coating is based upon anisocyanate component and an isocyanate-reactive component comprising apolyether polyol.
 22. The polyurethane encapsulated, slow releasefertilizer of claim 13 wherein said coating is about eight percent ofsaid coating by weight, and wherein said coating releases nutrient atrates comprising: about 2,300 ppm of nitrogen at 100 degrees Fahrenheitin about one day; about 5,200 ppm of nitrogen at 100 degrees Fahrenheitin about three days; and about 10,500 ppm of nitrogen at 100 degreesFahrenheit in about seven days.
 23. The polyurethane encapsulated, slowrelease fertilizer of claim 14 wherein said coating is about eightpercent of said coating by weight, and wherein said coating releasesnutrient at rates comprising: about 1,000 ppm of potassium at 100degrees Fahrenheit in about one day; about 4,000 ppm of potassium at 100degrees Fahrenheit in about three days; and about 19,000 ppm ofpotassium at 100 degrees Fahrenheit in about seven days.
 24. (canceled)25. The method of claim 1 wherein the forming further comprises: formingthe polyurethane encapsulated fertilizer particles comprising up toabout nine percent of said coating by weight.